Drilling into carbon fiber...???

Discussion in 'Luthier's Corner' started by silky smoove, Jan 27, 2005.

  1. silky smoove

    silky smoove Supporting Member

    May 19, 2004
    Seattle, WA
    This might be better placed in the luthier's corner, so if it needs to be moved, moderators, please do so.

    My 2000 Modulus Flea 4 is suffering from a bit of A string buzz. I've traced the problem to the nut, and its simply a result of not having enough downward pressure as the string "breaks" across the nut. I've had this problem on other basses before, and have always remedied the problem by simply adding a string tree for the A string. However, those were all basses that had wooden headstocks. So my question is this:

    Is there anything I should know about attaching a string tree to the headstock of my carbon fiber necked Modulus Flea bass? Typically I've just drilled a small pilot hole and then attached the string tree.... pretty simple stuff... but carbon fiber is a whole new world to me. Thanks in advance for any help that can be offered.
  2. giantjerk


    Jan 18, 2003
    Allen, TX
    You can drill into carbon fiber. I've done it on car hoods adn bike frames. IMO it does not have as much "give" as wood does. Depending upon the strength and density of the carbon fiber (layers) my experience is that it will have a tendency to split if the pilot hole diameter is too small.
  3. silky smoove

    silky smoove Supporting Member

    May 19, 2004
    Seattle, WA
    hmmmmm.... that scares me a bit (the tendency to split if the pilot hole is too small).... Thanks for the help, I'll see if I can't find a simpler solution.
  4. how about if you just don't drill the pilot hole too small? Seems like an ok thing to do. But does this stuff thread correctly? Or do you need to add some sort of adhesive or locktite so the stuff doesn't crumble around the threads?

    I ask because I simply do not know enough about this material.
  5. silky smoove

    silky smoove Supporting Member

    May 19, 2004
    Seattle, WA
    My only issue with drilling a larger pilot hole is that the screw on a string tree isn't that large. My fear is that if I drill it too big, the screw won't thread properly. If I drill it too small there's the potential for cracking. I had thought about some sort of threaded insert, but that seems overkill for a string tree. I'm open to other suggestions about alleviating open A string buzz at the nut. I've tried simply winding the string closer to the base of the tuning machine, but have had only minimal results......
  6. So mic the core diameter of the screwshaft...and you should be fine. :)
  7. silky smoove

    silky smoove Supporting Member

    May 19, 2004
    Seattle, WA
    mic? as in microphone? Not trying to be rude, but you lost me on that one my friend. Perhaps I'm just having a brain fart and didn't understand what you meant.
  8. I meant mic as in calipers. Measure the screw-shaft diameter, then pick a matching size bit. If you let the drill dwell slightly in the hole, it's create enough clearance for the shaft but not the threads, so they can do their job correctly.

    My question was whether you CAN thread properly into graphite material??? I imagine you can just fine, but I don't know how it reacts in general.
  9. Bass Kahuna

    Bass Kahuna

    Dec 3, 2002
    West Lafayette, Indiana
    Luthier, Custom Builder
    Make sure you're careful of the dust produced by drilling, cutting, or sanding carbon fiber. It is full of little "slivers" which make nasty slivers, and especially wear a mask and don't breathe the dust in, it is nasty in the lungs.
  10. silky smoove

    silky smoove Supporting Member

    May 19, 2004
    Seattle, WA
    Mon: Ah, I gotcha, it just didn't "click" the first time I read it. Thanks for the idea.

    Kahuna: Very helpful tip, thank you.
  11. Hmm - Graphite is very hard. Even with the correct sized pilot hole, I'm not sure that a self tapping screw is appropriate for that material.

    IMHO a better approach would be to drill and insert a knurled threaded insert with the approporiate glue into the headstock to accept a metal thread screw.

    Search for threaded inserts here:


    Good luck.
  12. phogchris

    phogchris www.scarsoflife.com

    May 27, 2000
    Boca Raton, FL
    The insert is a good idea, but you will also need to tap the hole first, you may even be able to do that by hand, you will need to buy the coresponding helicoil tap to the finished size of the screw. I would ditch the threaded wood screw you will have with the tree and buy a machine screw of the same size, tap the hole, put in the insert and screw the tree in. In this case you will not need any glue or anything as the screw and insert will hold without help. It is a bit involved, but the IMO, the best way to do it...or you could forgo the insert and just use a tap to create threads in the carbon fiber and then screw the tree in. It will be less sturdy, but will still be pretty good.
  13. I've had the same buzzing issue with graphite nuts, especially when I use thinner strings for altered tunings. Perhaps you could have someone simply file down the nut slot a little deeper, which would change your string angle ever so slightly?

    This stopped my string buzzing dead in its tracks. Also, and this probably isn't the case with your specific bass, but I have previously tracked down erroneous string buzzing to a loose bridge saddle screw OR a really bad string (or on a REALLY HORRIBLE BASS), both of which can be heard by means of horrible buzzing up in the nut area.

    Hope this helps!!!


  14. FenderMustang45


    Jan 29, 2005
    The screw won't thread right into the carbon fiber headstock. You could drill a larger (1/8") hole and glue in a wood dowel. Then drill your pilot hole into the dowel and you shouldn't have problems screwing your string tree into that. You should use a carbide bit to drill into the carbon fiber.
  15. Suburban


    Jan 15, 2001
    lower mid Sweden
    Personally, I would avoid wood screws into graphite. They might work fine, but also might not, due to the conical shaft shape of all wood screws I know of.

    I would go for "sheet metal screws", so called ST thread. They will cut well into the composite, without cracking when specified holes are made.
    Around here, they are available in any hardware store.

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